Sandy, Irene, Katrina... Hurricanes are fast becoming household names and have many people worried over the connection between extreme weather and the amount of greenhouse gases people are pumping into the atmosphere. No one can predict for sure what will happen decades or centuries from now as such gas concentrations increase. But scientists have a pretty good picture of what did happen in the past; greenhouses gases were released into the atmosphere in massive amounts at least once beforeâ€”around 56 million years ago.

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Sixty million years ago the Earth was already at least a few degrees warmer than it is today. At that point, there was little or no ice at the poles, and alligators were probably swimming in areas where polar bears roam today. But 4 million years later (56 million years ago) the world was about to undergo major changeâ€”in an event called the Paleocene-Eocene Thermal Maximum (PETM). During the PETM, massive amounts of greenhouse gases, probably in the form of methane that later oxidized to carbon dioxide, were spewed into atmosphere.

Scientists are still uncertain as to what had caused the release, but they do know that it happened in a short time periodâ€”probably a few thousand years. This CO2 explosion is similar to the one being produced by people now, which is why it is of such interest to scientists.

"The amount of carbon released in the PETM is thought to be similar to if we burn all of our fossil fuel reserves," says Phillip Jardine, who is studying the effects of PETM on plants as part of the Bighorn Basin Coring Project (BBCP) in Wyoming.

Together with the massive carbon release, the PETM is marked by another distinct featureâ€”a rise of 5-8 degrees Celsius in global temperatures, a rise scientists say would be catastrophic for human civilization today.